1. Field of the Invention
The present invention relates to means for the automatic flushing of toilets, urinals, and the like, in response to traffic flow into the toilet area.
2. Description of the Prior Art
A known auto-flush cistern for use over urinals and the like, comprises a cistern having a syphon outlet at the bottom and fitted with a suspended intermediate tank or a tray-like vessel having a large float valve fitted to its floor. The tray accommodates the float of a ball-cock that admits water directly to the tray. Incoming water will fill the tray to a point where the ball-cock closes. The water level in the tray will then be above a small orifice through a wall of the tray which allows water to fall to the cistern proper immediately below at a constant rate, the inlet head to the orifice remaining essentially constant under the regulation of the admitting ball-cock. The rate of fill of the cistern is determined by the tray orifice size used. The water level in the cistern rises to a point just below the lip of the outlet syphon tube at which point the large float valve fitted to the floor of the tray lifts allowing the tray contents to fall rapidly into the cistern, starting the syphon which in turn rapidly drains the cistern to the urinal causing the tray float valve to close and the tray to refill rapidly via the wide open ball-cock. The cycle then repeats itself at say 5 minute intervals of whatever maximum rate that is determined by the tray orifice. The purpose of the above system is to reduce water wastage i.e. to set a limit on the frequency of flushes regardless of mains-pressure etc., even though the mains cock be wide open.
This known device fulfills all of the requirements of hygiene, i.e., by regular flushing, but is extremely wasteful of water if (a) the urinal has irregular or intermittent use over long periods, or (b) is not used at all say from normal closing hours to the commencement of activities the next morning.
In my earlier Australian Pat. No. 522,747 there is disclosed a device for actuating the flushing action of an automatic flush cistern, and also an automatic flush cistern incorporating such a device, whereby an automatic flush cistern is adapted to flush in response to the entry of a person into a predetermined area (e.g. the entry of a person through the entrance door of a public toilet).
By means of my earlier automatic flush cistern, it is possible to retain the auto-flush cistern's ability to limit the flushes to say one every 5 minutes in peak use periods, but also to provide the ability to flush only when the system is triggered by occupation of the urinal area. In other words, with heavy traffic the urinal will be flushed at a maximum of say 5 minute intervals, in medium traffic say one occupation every 30 minutes, it will flush once after occupation, and with no traffic it will not normally flush at all until traffic recommences.
However, in my earlier automatic flush cistern, problems sometimes arose in circumstances where there was only infrequent use of the device and the small float (10) tended to stick to its seat and not be dislodged by the pulse of air from the door closer or other means designed to initiate or activate the cycle, but instead the air pulse would blow the water from the tubular tailpipe extension with the result that subsequent air pulses would not have the necessary blocking water in the tail pipe extension to cause the small float to be dislodged.
By substituting for the earlier tubular tailpipe extension a cup shaped extension with upwardly extended peripheral walls, a much greater quantity of water is stored in this area and a more permanent source of blocking water is maintained so that a subsequent air pulse is capable of dislodging the small float from its seat.
A further drawback with my earlier automatic flush cistern resulted from the requirement or preference of some government or public health authorities for an automatic flush cistern being adapted to flush automatically, say, at least every hour, in order to contain and control any odors which might normally eminate from the toilet or urinal drains during lengthy periods of infrequent or non use. With my earlier automatic flush cistern, regular flushing was achieved by virtue of a small "vee" notch being placed in the valve seat of the draft tube of the auto-flush device which provided for a small leak of water to flow through the draft tube from the upper compartment to the lower compartment of the cistern, eventually resulting in a flush cycle being initiated.
However, this modification of my earlier auto-flush cistern was originally designed for automatic flushing every 6 to 12 hours. To increase the automatic flush frequency to at least once every hour, required increasing the size of the "vee" notch to allow for a greater volume of water to pass therethrough. This created problems where allowance had to be made for the different capacities of cisterns in use and because of differences in water supply pressure. The larger "vee" notch required invariably allows sufficient air to enter the draft tube at the beginning of the flush cycle to cause the valve to unseat as the upper tray or upper compartment of the cistern refills, thus initiating another flush cycle ad infinitum. This, of course, is undesirable and results in wastage of water.